It is a conventional practice to reduce pulsation of torque produced by a load like an AC motor, for example, connected to a power converter (inverter) by detecting a DC voltage of rectification means for rectifying AC power, correcting an output voltage of the inverter using information on this DC voltage, and suppressing pulsation of the output voltage of the inverter caused by periodic pulsation of the aforementioned DC voltage. As a result of recent advance in technology, it is now required that torque output by this kind of AC motor, for example, using an inverter be controlled more and more precisely.
To cope with such a requirement, the prior art discloses an inverter output voltage correcting apparatus for suppressing output voltage pulsation of an inverter caused by DC voltage pulsation due to an imbalance of phase-to-phase voltages of a three-phase AC power supply or a reduction in capacity of a capacitor of rectification means, for instance. This inverter output voltage correcting apparatus corrects an output voltage command value according to variations in DC voltage by using a microcomputer and controls the inverter by using the output voltage command value thus corrected, the inverter output voltage correcting apparatus including detected DC voltage value estimation means for estimating a detected DC voltage value at a waveform output timing from a detected DC voltage value obtained at a point of a preceding carrier interrupt and that obtained at a point of a present carrier interrupt (Patent Document 1, for example).    Patent Document 1: Japanese Laid-open Patent Application No. 2004-147433